/*
 * Copyright (c) 2009 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup bd
 * @{
 */

/**
 * @file
 * @brief File-backed block device driver
 *
 * Allows accessing a file as a block device. Useful for, e.g., mounting
 * a disk image.
 */

#include <stdio.h>
#include <unistd.h>
#include <ipc/ipc.h>
#include <ipc/bd.h>
#include <async.h>
#include <as.h>
#include <fibril_sync.h>
#include <devmap.h>
#include <sys/types.h>
#include <errno.h>
#include <bool.h>
#include <task.h>

#define NAME "file_bd"

static size_t comm_size;
static FILE *img;

static dev_handle_t dev_handle;
static fibril_mutex_t dev_lock;

static int file_bd_init(const char *fname);
static void file_bd_connection(ipc_callid_t iid, ipc_call_t *icall);
static int file_bd_read(off_t blk_idx, size_t size, void *buf);
static int file_bd_write(off_t blk_idx, size_t size, void *buf);

int main(int argc, char **argv)
{
	int rc;

	printf(NAME ": File-backed block device driver\n");

	if (argc != 3) {
		printf("Expected two arguments (image name, device name).\n");
		return -1;
	}

	if (file_bd_init(argv[1]) != EOK)
		return -1;

	rc = devmap_device_register(argv[2], &dev_handle);
	if (rc != EOK) {
		devmap_hangup_phone(DEVMAP_DRIVER);
		printf(NAME ": Unable to register device %s.\n",
			argv[2]);
		return rc;
	}

	printf(NAME ": Accepting connections\n");
	task_retval(0);
	async_manager();

	/* Not reached */
	return 0;
}

static int file_bd_init(const char *fname)
{
	int rc;

	rc = devmap_driver_register(NAME, file_bd_connection);
	if (rc < 0) {
		printf(NAME ": Unable to register driver.\n");
		return rc;
	}

	img = fopen(fname, "rb+");
	if (img == NULL)
		return EINVAL;

	fibril_mutex_initialize(&dev_lock);

	return EOK;
}

static void file_bd_connection(ipc_callid_t iid, ipc_call_t *icall)
{
	void *fs_va = NULL;
	ipc_callid_t callid;
	ipc_call_t call;
	ipcarg_t method;
	int flags;
	int retval;
	off_t idx;
	size_t size;

	/* Answer the IPC_M_CONNECT_ME_TO call. */
	ipc_answer_0(iid, EOK);

	if (!ipc_share_out_receive(&callid, &comm_size, &flags)) {
		ipc_answer_0(callid, EHANGUP);
		return;
	}

	fs_va = as_get_mappable_page(comm_size);
	if (fs_va == NULL) {
		ipc_answer_0(callid, EHANGUP);
		return;
	}

	(void) ipc_share_out_finalize(callid, fs_va);

	while (1) {
		callid = async_get_call(&call);
		method = IPC_GET_METHOD(call);
		switch (method) {
		case IPC_M_PHONE_HUNGUP:
			/* The other side has hung up. */
			ipc_answer_0(callid, EOK);
			return;
		case BD_READ_BLOCK:
		case BD_WRITE_BLOCK:
			idx = IPC_GET_ARG1(call);
			size = IPC_GET_ARG2(call);
			if (size > comm_size) {
				retval = EINVAL;
				break;
			}
			if (method == BD_READ_BLOCK)
				retval = file_bd_read(idx, size, fs_va);
			else
				retval = file_bd_write(idx, size, fs_va);
			break;
		default:
			retval = EINVAL;
			break;
		}
		ipc_answer_0(callid, retval);
	}
}

static int file_bd_read(off_t blk_idx, size_t size, void *buf)
{
	size_t n_rd;

	fibril_mutex_lock(&dev_lock);

	fseek(img, blk_idx * size, SEEK_SET);
	n_rd = fread(buf, 1, size, img);

	if (ferror(img)) {
		fibril_mutex_unlock(&dev_lock);
		return EIO;	/* Read error */
	}

	fibril_mutex_unlock(&dev_lock);

	if (n_rd < size) 
		return EINVAL;	/* Read beyond end of disk */

	return EOK;
}

static int file_bd_write(off_t blk_idx, size_t size, void *buf)
{
	size_t n_wr;

	fibril_mutex_lock(&dev_lock);

	fseek(img, blk_idx * size, SEEK_SET);
	n_wr = fread(buf, 1, size, img);

	if (ferror(img) || n_wr < size) {
		fibril_mutex_unlock(&dev_lock);
		return EIO;	/* Write error */
	}

	fibril_mutex_unlock(&dev_lock);

	return EOK;
}

/**
 * @}
 */